Return type for `detailedDiff`

Update return type of `detailedDiff` to reflect the static top level properties:

Current:
```
export function detailedDiff (originalObj: object, updatedObj: object): object
```

Proposed:
```
type DetailedDiff = {
  added: object;
  deleted: object;
  updated: object;
};

export function detailedDiff (originalObj: object, updatedObj: object): DetailedDiff
```